Pop popcorn until you have 9 cups of popped popcorn and place in a large bowl
In a medium saucepan melt butter, peanut butter, chocolate chips and stir in vanilla once mixture is all melted
Slowly pour mixture over popcorn and add powdered sugar and toss until the popcorn is evenly coated. Spread mixture out onto baking sheets to set.
A simple method I have used for coating all the popcorn in the powdered sugar is to place the popcorn that has the chocolate and peanut butter mixture on it in a NEW paper grocery bag and gently shake the bag to help distribute the powdered sugar easier.